thermal/intel_powerclamp: stop sched tick in forced idle

With the introduction of play_idle(), idle injection kthread can
go through the normal idle task processing to get correct accounting
and turn off scheduler tick when possible.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>